Electric-discharge device



June 28, 1960 E A CQLSQN ELECTRIC-DISCHARGE DEVICE Filed Sept. 29, 1958 fault? INVENTOR EDWARD A. COL SO N A 7 TORNEVS United States Patent ELECTRIC-DISCHARGE DEVICE Edward A. Colson, Hillsboro County, N.H., assignor to Edgerton Germeshausen & Grier Inc., Boston, Mass, a corporation of Massachusetts Filed Sept. 29, 1958, Ser. No. 763,982

3 Claims. (Cl. 313-198) medium Within which an electrical discharge may pass to produce a flash of illumination. The environment within which the flash tube is to be operated determines, in many cases, the material from which the'flash-tubeenvelope ismanufactured. As is disclosed, for example, in United States Letters Patent No. 2,277,698, issued on March 31,

1942, to'Kfenneth I. Germeshau sen, the operator may sometimes have to beprotected from possible fracture of the flash lamp by enclosing the same in an outer glass or other housing." If a flash lamp,moreover, is to be operated in liquids, it must also be protected from its environ ment, as discussed, for example, in co-pending application, Serial No. 437,647, filed June 18, 1954, by Harold E. Edgerton, for Underwater Flash-Producing System, now Patent No. 2,872,622.

The present invention is primarily directed to the problem of providing satisfactoryelectric-discharge devices, including flash tubes and the like, that may operate under more adverse environmental conditions, such as in. a potentially explosive atmosphere orat extreme altitudes where prior-art flashlamps have been found to be unsuitable. s Y

A further object is to provide a novel flashtube and thellike that may be of extremelysmall dimensions, as wel Other and further objects will 1;. explained hereinafter,

and will be more particularly pointed out in connection with the appended claims. V I v ,In summary, from perhaps its broadest aspect, the in- Patented June 28, 1960 V 2 are shown in the form of a pair of rod-like electrodes 5 and 7, spaced at opposite ends of the flashtube envelope 1 and extending through seals at the end walls thereof, as at 9 and 11, respectively. This construction may, as an illustration, be of the type described in United States Let- V ters Patent No. 2,756,361, issued to the said Kenneth J.

Germeshausen, on July 24, 1956; or in copending application, Serial No. 5 88,906 of the said Harold E. Edgerton, filed June 1, 1956, for Flash Tube and Apparatus. The electrodes 5 and 7 are shown preferably disposed substantially along the axis of the tubular envelope 1 and are provided with lead extensions 9' and 11' adjacent but external to the envelope]. A preferably externally disposed tn'gger electrode 13, comprising one or more turns of wire, may also be employed to assist in the initiation of the electrical discharge within the gaseous chamber 3 between the principal electrodes Sand 7'in well-known manner,'as described in the said United States Letters Patent and applications.

As an illustration, in the case of the said FX-4 flashtube, a capacitor C may be chargedfrom a direct-current voltage source, .+,=-,;-through a charging resistor or other impedance R supplying energy-for producing the main flash dischargebetween the principal electrodes 5;:

and 7 to which, it is connected. The voltage stored upon the capacitor .C, however, is not of itself 'suflicient to produce the before-mentioned electrical discharge through,

the gaseous medium 3 until atrigger voltage is applied between, for example, the trigger electrode 13 and the cathode principal-electrode 7, as by means of the secondary winding Sofa trigger transformer T. -The trigger impulse for energizing the trigger transformer T may be produced-by closing a switch'S, thereby to discharge a trigger capacitor c' that has normally become charged from the positive potential source terminal through a charging resistor or other impedance R and the primary Winding P of the trigger transformer T. The closure of the switch S causes the capacitor C to discharge its voltage through the primary winding P, producing a trigger pulse.;-that is conveyed to the secondary winding S and ,5 thence to the trigger electrode 13, thereby to initiate the a discharge chamber provided With electrodes between which a discharge may pass in the chamber and electrode lead connections extending external to the chamber, the chamber and at least the portions of the externallyextending electrode lead connections adjacent thereto being imbedded within a block of electrically insulative light-transparent material. Preferred details are hereinafter set forth.

The invention will now be described in connection with the accompanying drawing, the singlefigure of which illustrates the invention in preferred form connected with a preferred electronic circuit for operating the same, though other types of circuits may also be employed.

Referring to the drawing, a flash tube'is shown comprising a preferably, though not essentially, tubular glass or other light-transmitting envelope 1, the space Within which defines a gas-discharge chamber 3 filled with any desired gas, such as xenon gas, as employed, for example, in the type FX-4 flashtube, manufactured by Edgerton, Germeshausen & Grier, Inc. The principal electrodes within the gaseous chamber 3 defined by the envelope 1 discharge of'the main flash capacitor C between the principal. electrodes and 7.' Other 'typesof flash-producing 1 circuits may, ofcourse, :be employed, as discussed in the said Letters Patent and applications.

. hen'a flash tube subjected to the before-mentioned unusual environmental conditions, it is generally found to be too fragile or otherwise unsatisfactory.- 'As an illustration, flashtubesof'thischaracter require a relatively high starting voltage. This is no particular problem under ordinary laboratory or other operating conditions.

This does become a serious problem, however, if the tube 1 must be operated in an explosive atmosphere, or at extreme altitudes, or under other unusual conditions. Flashtubes, as another example, may also be required to take photographs within a gas well, or Within the human stomach for diagnostic purposes, or in some other equally unusual environmental condition. The tube, moreover, may be subjected to extreme mechanical shock and vibration, as in connection with its use in modern aircraft and the like.

It has been discovered, however, that a particular treatment of the tube 1 will enable it to be used in all such unusual environmental circumstances. That treatment involves the incapsulating or imbedding of the flashtube '1 Within a block of light-transparent mechanically rugged trode extensions 9' and 11' constituting part of the electrode-lead connections that pass through the end seals 9 and 11 of the tube 1, and at least a portion of the further lead connections 9", 11" and 13' associated with the fiashtube 1, all within the block 15, the eifects of mechanical shock or heavy vibration, the danger of explosion, the effects of extreme temperature variations and other undesirable environmental conditions are completely overcome.

In the particular illustrated construction, the further lead connections 9", 11" and 13 are shown carried substantially parallel to the axis of the tube 1, though to the side thereof, through the preferably substantially cylindrical external block 15 to a common lower end thereof. They are there connected with insulation-covcred terminal lead connections 2, 4 and 6, the insulation of which is preferably of a material, such as vinyl insulation, that may be well bonded to the material employed for the block 15.

It has been found that the before-mentioned epoxy resin, provides insulation of the glass tube structure 1 against severe thermal shock. The tube 1, thus incapsulated' was operated from a temperature environment of 55 centigrade to up to +95 centigrade, repeatedly, and without causing any mechanical damage. Such a tube has also been operated successfully when immersed in water and other liquids, and even to photograph the inside of a gas well where explosion was of extreme concern. Such 'fiashtubes have also been successfully operated within the block 15 in high-flying aircraft at altitudes of up to 70,000 feet, for the purpose of-producing flash records of moving dials or meters and the like, and was found well to withstand the shock and vibration requirements produced by such operation.

It will also be observed that the block 15 may obviously be dimensioned such that it does not appreciably increase the space occupied by the fiashtube 1. Extremely small light sources that must be subjected to extreme environmental conditions may thus be provided. The FX-4 fiashtube 1, before-mentioned, thus embodied an epoxy-type resin block 15, for example, and operated at a rate of one flash per second with an energy input of about A; of a watt-second will normally operate with a minimum life of 4,000 light flashes. If greater life is required, of course, less energy per flash and a lower repetition rate may be employed. If, moreover, the block 15 is formed so as to have its own internal chamber 1 as a cavity therein, with appropriate electrodes 5, 7, etc., the effects of such environmental conditions may also be mitigated against, though it is preferred, for purposes of manufacture, and because flash lamps have other uses in other environmental conditions, to employ the separate fiashtube envelope 1, as described; it being understood, however, that the term chamber, as used herein, is intended to embrace both such types of construction.

Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

l. A gaseous-discharge device having a fiashtube comprising a light-transparent envelope defining a gas-filled discharge chamber provided with a pair of spaced principal electrodes between which a discharge may pass in the chamber, electrode extensions extending from said principal electrodes, respectively, through seals in said envelope and externally of said envelope, and electrodelead connections extending from said principal electrode extensions externally of the envelope, the envelope, the electrode extensions, and at least the portions of the electrode-lead connections near the envelope being embedded within a block of electrically insulative lighttransparent material, said electrode extensions being supported solely by said envelope seals and by the material of said block.

2. The device of claim 1, further comprising an auxiliary trigger electrode external to the envelope for initiating the discharge, and electrode-lead connections extending from said trigger electrode, the trigger electrode and its lead connections being embedded within said block of material.

3. The gaseous-discharge device of claim 2, said envelope being tubularand said block being substantially cylindricahsaid principalelectrodes extending substantially along the axisof said envelope, said lead connections extending in part along the length of said envelope within said block material and terminating at one end of'said block in insulation covered terminal lead connections, the insulation material being bonded to the block material.

References Cited in the file of this patent UNITED STATES PATENTS 2,031,722 Lowe et al Feb. 25, 1936 2,293,529 Bedtord Aug. 18, 1942 2,478,908 Edgerton Aug. 16, 1949 2,538,577 McCarthy Jan. 16, 1951 2,590,821 Kiser Mar. 25, 1952 2,691,120 Barber Oct. 5, 1954 2,825,000 Beeson Feb. 25, 1958 OTHER REFERENCES Potted Subassemblies for Subminiature Equipment, by W. G. Tuller, Electronics, September 1949, pages 104 and 105.

Electronic Preserves, by F. P. Franklin and M. Weinberg, Scientific American, December 1947, pages 258 to 260. 

